1. Field of the Invention
The present invention relates to a capacitive load driver for driving a capacitive load such as an EL (electroluminescence) element, and particularly, to a technique of improving the power efficiency of such a capacitive load driver.
2. Description of the Related Art
A problem that arises when an EL element is pulse-driven is that the charge of a parasitic capacitance of the EL element is entirely abandoned at the time of discharge, to deteriorate power efficiency. To deal with this problem, some related art partly collects the charge of the parasitic capacitance with a charge collecting capacitor and reuses the collected charge to improve power efficiency.
For example, Japanese Unexamined Patent Application Publication No. H09-322560 (Document 1) discloses a capacitive load driver of improved power efficiency. This related art connects the charge and discharge electrodes of an EL element to a capacitor through a switching circuit. When discharging the EL element, the related art partly transfers the charge of the EL element to the capacitor and discharges the remaining charge of the EL element. Thereafter, the related art returns the transferred charge from the capacitor to the EL element when charging the EL element.
This related art partly reuses the charge accumulated in the EL element, to improve power efficiency by the reused charge.